A pretty short game, but the puzzles are interesting and well made. Really liked the last one, in particular! Also, I agree with some other comments, and sounds would make this game a lot more polished, which is something I believe you could include in your mobile version.
Also, if you don't mind, I suggest prototyping new stages using PuzzleScript. I'm not sure how easy it is to design puzzles in Unity, but in PuzzleScript it is very easy, and even fun. Of course, it is mostly for prototyping, so its graphics are pretty...simple.
Once again, nice job on your game!